Partial-ring positron emission tomography (“PET”) systems have been gaining use in breast imaging and radiation therapy applications. For breast imaging, partial-ring PET systems allow detectors to be positioned closer to the patient's anatomy, which improves sensitivity compared to full-ring detectors. Likewise, the opening in the partial-ring detector assembly allows clinician access to the patient (e.g., to perform a biopsy). Similarly, for radiation therapy applications, partial-ring PET systems provide an opening through which a treatment beam can be delivered to a patient while that patient is positioned in the imaging field-of-view of the PET system. This arrangement allows for verification of radiation beam delivery immediately after cessation of the radiation beam, and without needing to move the patient.
The limited view angle coverage associated with partial-ring detectors results in an incomplete angular view sampling, which causes artifacts in image reconstruction. Time-of-flight (“TOF”) PET can be used to improve the image quality achievable with partial-ring PET systems because the number of angular views necessary for an artifact-free image reconstruction can be decreased based on the increased temporal resolution achievable with TOF PET techniques.
Thus, there remains a need for appropriate image reconstruction techniques that can allow for the benefits of TOF PET to be applied to limited angle applications.